The exposure and toxicity of pesticides to amphibians

Amphibians and pesticides
Given this potentially punctuated pattern of risk, interpretation of the information may be problematic
as the potential risk will depend on the activity state of the animal. It may therefore be necessary to
make a worst case assessment and assume the animal is on the field for whatever period it spends in
that habitat (or a high percentile value), rather than make a more realistic assessment of the probability
that the animal is there at all.
1.3.3. Timing of terrestrial activity in relation to pesticide applications
Clearly the risk of exposure depends on the use of habitats treated with pesticides at the time of
application and a period after this depending on the persistence of the compound or the application of
subsequent treatments. While the potential coincidence of amphibians and pesticide treatments can be
predicted using data on the timing of terrestrial activities and pesticide treatments, this is likely to be a
very approximate estimate given the issues listed above (i.e. patterns of fine scale use of treated areas).
A recent study (Berger et al. 2011a) used fence traps to monitor migration of adults from winter
quarters to spawning waters. As part of this study they determined the proportion of the population
that coincided with soil working and sowing, the application of mineral and organic fertilisers and the
application of plant protection products and growth regulators.
They found that herbicide applications to fodder peas, oats, sunflowers and blue lupins sometimes
coincided with high levels of amphibian activity. For example, in one year 85% of the population of
spadefoot toads (Pelobates fuscus) were active on the land at the time of an application of herbicide to
fodder peas, while 20-50% of the population activity of fire-bellied toads (Bombina bombina), moor
frogs (Rana arvalis) and great crested newts (Triturus cristatus) coincided with the application of
herbicides to other crops.
High levels of coincidence of activity of all four species with application of fungicides to winter rape
were also observed. For other winter cereal crops, only those species active later in the year (spadefoot
toads and fire-bellied toads) had high levels of coincidence with applications. Average levels of
activity of greater than 30% of the population were recorded.
Between 20 and 40% of the populations of the migration on land of these species coincided with the
application of insecticides to winter rape. In one year, the coincidence of spadefoot toads with such
applications was almost 90%. Application of insecticides to winter wheat did not overlap with the
period during which amphibians were migrating to spawning waters.
Over 50% of the activity of fire-bellied toads coincided with applications of growth regulators to
winter rye in one year with lower levels of coincidence (up to 25%) for applications to triticale.
Coincidence of great crested newts and spadefoot toads with applications to winter rye and all three
species with applications to winter wheat were also around this lower level.
1.4. Species information
Information potentially useful for future risk assessments on selected species associated with
agricultural habitats was collated. The species for which detailed information were selected on the
basis of their association with arable land, their distribution (e.g. present in all zones) and appearnace
in studies of the use of agriculural habitats. The selected species were the great crested newt (Triturius
cristatus), the smooth newt (Lissotriton vulgaris), the common frog (Rana temporaria), the common
toad (Bufo bufo), the common tree frog (Hyla arborea), the natterjack toad (Hyla arborea) and the
common spadefoot (Pelobates fuscus). This data can be found in Appendices B to H.
Supporting publications 2012:EN-343 23
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